1. Field of the Invention
This invention relates to a mower unit. Such a mower unit has a housing, and a pair of cutting blades arranged in the housing to be rotatable, respectively, about vertical axes supported by the housing. The pair of cutting blades are driven to rotate in opposite directions.
2. Description of Related Art
A conventional mower unit as noted above is disclosed in JP 2001-45828, for example. The mower unit shown in this document has three blades arranged transversely in a housing, and a vacuum plate located forwardly of the three blades. Of the three blades, the blade located in the middle and the blade located at right-hand side are driven to rotate in opposite directions. The vacuum plate has a curved discharge portion extending to a region between a rotation region of the middle blade and a rotation region of the right-hand blade. The curved discharge portion serves as a baffle for the middle blade and right-hand blade acting as a pair of rotary cutting blades, to guide winds flowing from the middle blade and right-hand blade. The length of the curved discharge portion lying between the rotation regions is substantially the same over a full length (total height) of the curved discharge portion in the vertical direction of the blade housing.
In a mower unit having a pair of rotary cutting blades arranged transversely of a blade housing to be rotatable in opposite directions, a grass discharge opening may be formed at one lateral end of the blade housing to enable a side discharge operation. The grass discharge opening may be closed, or may not be formed at one lateral end of the blade housing, to enable a mulching operation. That is, with the grass discharge opening formed, a side discharge operation can be carried out to discharge grass clippings cut by each rotary cutting blade from the lateral end of the blade housing to areas laterally outward of the mower unit. With the grass discharge opening closed, or not formed at one lateral end of the blade housing, a mulching operation can be carried out to discharge grass clippings cut by each rotary cutting blade from the bottom of the blade housing to areas below the mower unit. In this case, when the conventional technique relating to the baffle is employed, the side discharge operation is liable to low efficiency of discharging grass clippings to areas laterally outward of the mower unit, or the mulching operation is liable to low efficiency of shredding and dispersing grass clippings.
In the case of side discharge operation, the grass clippings cut by the rotary cutting blade far from the grass discharge opening, of the pair of rotary cutting blades, join the grass clippings cut by the rotary cutting blade near the grass discharge opening, to be discharged together from the grass discharge opening. For this purpose, the grass clippings cut by the rotary cutting blade far from the grass discharge opening should desirably flow smoothly into the rotation region of the rotary cutting blade near the grass discharge opening. In the case of mulching operation, it is desirable that the grass clippings cut by each rotary cutting blade circulate in the rotation region of the rotary cutting blade, so that the grass clippings may be shredded by each rotation cutting blade and discharged below the rotation region of the rotary cutting blade.
However, in the case of side discharge operation, to make it easy for the grass clippings produced in the rotation region of the rotary cutting blade far from the grass discharge opening to flow into the rotation region of the rotary cutting blade near the grass discharge opening, it is necessary to reduce the length of the baffle extending into the space between the rotation regions so that the baffle may not obstruct the inflow. Then, in time of mulching operation, the wind from each rotary cutting blade flows toward the rotation region of the other rotary cutting blade in locations spaced from the baffle. The winds from the rotary cutting blades join in a location where the two rotation regions communicate. Thus, the grass clippings cut by each rotary cutting blade can hardly circulate in the rotation region of the rotary cutting blade.
On the other hand, in the case of mulching operation, to make it easy for the wind from each rotary cutting blade to flow separately toward the rotation region of that rotary cutting blade also in the location spaced from the baffle, and for the grass clippings cut by each rotary cutting blade to circulate in the rotation region of that rotary cutting blade, it is necessary to increase the length of the baffle extending into the space between the rotation regions so that the baffle may guide the winds reliably. Then, in time of side discharge operation, the grass clippings cut by the rotary cutting blade far from the grass discharge opening will have difficulty in flowing into the rotation region of the rotary cutting blade near the grass discharge opening.